Her dog is bred from working lines, her dog is not a working dog. When a working breeder breeds a litter, they never keep the entire litter. They keep the one or two pups with the most potential and sell the remainder of pups normally to sport homes or very experienced pet homes. Some times when they have trouble finding appropriate homes, the standards for what an appropriate home may be lowered and some pups from working lines with lower then average drives do make wonderful pets even for those with less experience (although that in general is an exception not the rule).

Generally, puppies are briefly tested for basic characteristics of what would make them appropriate for police work, then they are raised, socialized, and given very minimal training until they are mature and begin to show their true genetic potential. These are referred to as green dogs and are generally about a year old. Then they are tested again more extensively for their potential to do police work and what type and if they pass they go on to specialized training. It costs thousands of $ and extensive man hours to train a police dog, so not just any potential candidate makes it into the program. No one will waste their time on a dog if they just might make it. Very few dogs, even from working lines have what it takes to become a police dog. It really takes an extremely special dog.

"My 6 month old GSD has got serious aggression
Issues. He is a working dog, both his parents
Are police dogs. He was given raw meat "

I copy this from the OP first comment. They wrote their dog is a 'working' dog. That is why I called it a working dog.

I know how it works with working dogs, I posted that about dogs used at service dogs ,it works the same way. It is hard to know just how some puppies will turn out, and it cost a lot of money to train hearing and seeing eyes dogs. If a dog it not a good candidate it given up as a pet. I was wondering if the puppy had started some training to be a police dog and was not measuring up to par.
I hope the OP will be able to find way to train their dog so they will keep him. He is a beautiful and GS are so smart and with the right trainer the dog should learn fast.